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Biomedical subjects

P Krag

Publications and source records attributed to P Krag.

6 recordsLinked to original sources
PubMed1994

Is the modality-shift effect specific for schizophrenia patients?

Several studies have found that the reaction time of schizophrenia patients is longer when successive imperative stimuli are of different modality (e.g., light followed by sound) than when they are identical (e.g., sound followed by sound). This effect is called the modality-shift effect. In this study, the reaction times of 175 persons were analyzed: 54 schizophrenia patients, 33 patients with mood disorders, 13 alcoholics, 17 patients with rheumatoid arthritis, 13 patients with internal diseases, and 45 normal controls. The results indicated that a shift from light to sound stimuli lengthened the reaction time for schizophrenia patients considerably more than for alcoholics, patients with rheumatoid arthritis, patients with internal diseases, or normal controls. No difference was found between the reaction times of schizophrenia patients and patients with mood disorders.

Adult↗
PubMed1977

A method for measurement of the bubble formation threshold in biological liquids.

Liquid under pressure is saturated with a given gas, such as argon, nitrogen, or air, by circulation through a column of gas exchangers. A sample of the gas-saturated liquid is isolated in a test chamber, the volume of which can be increased by means of a moving piston. The piston motion is cyclical with a variable frequency. Pressure in the test chamber is measured by means of a capacitive pressure pick-up. When the volume increase of the gas-saturated liquid in the test chamber is compensated for by the development of gas phase bubbles, the pressure decrease will stop; the recording device will show a pressure plateau, or a dip in the pressure-time course, depending on the velocity of the growth of the bubbles. Bubble formation threshold was independent of the frequency of the piston movement within frequency limits from 1 Hz down to 10(-3) Hz. Most experiements were carried out at a single frequency of 0.5 Hz. This new method appears to have advantages over previous ones.

Decompression↗
PubMed1971

The international reference preparation of influenza virus haemagglutinin (type A).

This paper describes the international collaborative assay that led to the establishment in 1967 of the International Reference Preparation of Influenza Virus Haemagglutinin (Type A) and the studies completed during the following years on the use of the preparation for evaluating the haemagglutinin content of 46 influenza virus vaccines in terms of international units. The WHO Expert Committee on Biological Standardization (1967) defined the International Unit as 0,09361 mg of the International Reference Preparation.Altogether 14 laboratories in 12 countries took part in one or both studies, using a total of 24 methods (HA titrations and, in a few cases CCA titrations). Major differences in the HA titres were found between laboratories, while the potencies (the haemagglutinin content values) relative to the International Reference Preparation were free from most of these differences. Haemagglutination titres varied over a range factor up to 50, while the corresponding relative "potencies" varied with a factor of only 2. The CCA method used in a few laboratories gave results close to the lowest haemagglutination titres and showed relatively small variations between laboratories. The analyses of variance disclosed differences in the variation within laboratories, but for the majority of the laboratories the variation allowed an overall estimate of a standard error.The calculation of haemagglutinin content (in IU) from relative potencies is described. Advice is given on the selection, preparation, and titration of a local reference vaccine with a view to expressing its haemagglutinin content in international units.The test results with 46 local vaccines are also given. The deviations of the relative potencies from the average per vaccine showed a distribution with eight major discrepancies instead of the expected one. The background for these cases is discussed.

Agglutination Tests↗
PubMed1970

International reference preparation of rheumatoid arthritis serum.

The National Institute for Medical Research, London, England, was requested by the WHO Expert Committee on Biological Standardization to arrange a collaborative study of the serum pool they had obtained, to determine its suitability to serve as an international reference preparation of rheumatoid arthritis serum. A batch of this serum was assayed by 11 laboratories in 7 countries against 30 test preparations. On the basis of the results obtained, the serum has been established as the International Reference Preparation of Rheumatoid Arthritis Serum and the International Unit of Rheumatoid Arthritis Serum has been defined as the activity contained in 0.171 mg of the international reference preparation.A description is also given of the British reference preparation of rabbit antibody to sheep red blood cells (amboceptor) and this material was also tested in the collaborative study.

Animals↗
PubMed1965

International collaborative assay of the international reference preparation of anti-yellow-fever serum.

A yellow fever immune serum was established in 1962 by the WHO Expert Committee on Biological Standardization as the International Reference Preparation of Anti-Yellow-Fever Serum, intended to serve as an immune reference serum in the mouse protection test used in the control of yellow fever vaccines.Before its establishment as the International Reference Preparation, the proposed material was assayed in eleven laboratories in ten countries against a number of other immune and non-immune sera, and was found stable. Neutralization test results were consistent and the relative potency was sufficiently high. This paper not only reports on the collaborative assay, but also discusses errors in the testing method and problems connected with the distribution of mouse deaths during the observation period and with the preparation of dilutions.

Biological Assay↗